1. Field of the Invention
The present invention relates to an electric operation apparatus, and particularly, to an electric knife which can immediately detect an undesirable situation for a patient and make a proper treatment responsive thereto, when an undesirable situation occurs in a surgical operation or a treatment using an endoscope.
2. Description of the Related Art
In surgical operations and treatments using an endoscope, it is important that operations and treatments are performed securely, and that safety is ensured for patients.
In the following, several conventional techniques will be explained which take into consideration such safety.
At first, a first conventional technique will be explained. For example, a mono-polar method is known as an output for an electric knife. According to this method a high frequency current outputted from a knife end is collected through an electrode called a counter electrode plate having a large area. A counter electrode plate is normally attached on body surfaces of a femoral region or buttocks of a patient, and is connected to the electric knife apparatus by a cable. In addition, when a situation occurs in which a high frequency current cannot be properly collected by the counter plate, a burn is caused at an undesirable portion, and therefore, a monitor circuit is provided to avoid such a situation.
Counter plates for an electric knife are roughly classified into two types. One of the types is a counter plate 403 of a mono-polar type, as shown in FIG. 1A, in which an 401 is provided with a sheet electrode 402, and in this counter plate 403, the electrode 402 is connected with two codes 404, thereby forming a loop.
Another type is a counter plate 407 of a separate type, as shown in FIG. 1B, in which two or more electrodes 406 are provided at intervals on a sheet 405 so as to form a sheet, and the electrodes 406 are respectively connected with codes 408. Respective electrodes 406 are attached to a patient, thereby to form a loop including the body surface of a patient.
As for a monitor circuit for detecting whether or not a counter plate is correctly attached, there have been methods which respectively correspond to the counter plates of the two types described above. Specifically, in a monitor circuit for a counter plate of a mono-polar type, a slight voltage is applied to a loop formed by two codes 404 and an electrode 402, and the continuity of a loop is detected, depending on whether or not a current flows, thereby to determine presence or absence of a disconnection of the codes 404 or a defective connection to an electric knife apparatus.
In addition, in a monitor circuit for a counter plate of a separate type, a slight direct current or alternating current is made flow between respecting electrodes 406, and the resistance or impedance between respective electrodes 406 is detected, thereby to determine the contact condition of the counter plate 407 with a patient.
Therefore, in order that both of the two types of counter plates 403 and 407 can be used, a conventional electric knife apparatus adopts a monitor circuit for a counter plate of a separate type, which has been modified to be applicable to a counter plate of a mono-polar type, and to be switched in accordance with the type of counter plate to be used. For example, there has been proposed a method in which the type of a counter plate is identified by making the shapes of connectors of the counter plates 403 and 407 different (cf. Japanese Patent Application KOKAI Publication No. 64-76846), and in which a user pushes selection switches corresponding to the counter plates.
Next, a second prior art technique will be explained. In general, in an electric knife apparatus, a high frequency of several hundreds KHz is used and theoretically, a high frequency current flows from an active line to an organic tissue. Then, this current is collected by the electric knife itself through a counter plate and patient codes. The high frequency current which has thus flowed through the route as described above functions to make a high frequency treatment effect.
However, since signals to be dealt with are of a high frequency as has been described above, a current flows to a route passing through the so-called ground under influences of a floating capacity in the air and a bonding capacity. There may be a case in which a leakage current of a high frequency which thus flows through the ground becomes a factor which causes an unintended burn in a patient or an operator.
In Japanese Patent Application KOKOKU Publication No. 61-32016, a safety system for an electric knife apparatus has been proposed which safely and securely performs a high frequency treatment. This is a system which detects a current IA flowing through an active line and a current IP fed back through a patient code from a counter plate, and which calculates a ratio of IP/IA. If the calculation result is lower than a predetermined value, this safety system determines that a high frequency leakage current has increased to a dangerous level, and controls the output.
Meanwhile, several electric knife apparatuses used in this kind of surgical operation comprise a spray coagulation function. The spray coagulation function means a technique in which a high voltage is applied between a treatment electrode portion and a patient tissue, with them kept apart from each other, thereby to obtain discharging, so that blood is coagulated. As a result of this, high coagulation performance can be effected at over a wide range of portions. Normally, to arrest bleeding, an electrode is brought into contact with a bleeding portion, and blood is coagulated by a heat effect of a high frequency current. In this case, blood or tissues may stick to the electrode portion, and the performance of an electric knife may be degraded. Otherwise, when the electrode is removed from tissues, a coagulating portion sticking to the electrode may be pealed off and may result in bleeding again.
However, since a coagulation treatment can be carried out with the electrode and tissues kept apart from each other in this kind of spray coagulation function, as has been described above, it is possible to overcome the above mentioned drawbacks which occur in normal blood coagulation.
Further, a third prior art technique will be explained. In recent years, an electric operation apparatus such as an electric knife utilizing a current of a high frequency (several hundreds kHz) and a high voltage (several hundreds to several thousands V) has been widely put into practical use. In an operation using this kind of electric operation apparatus, safety is particularly significant.
An electric operation apparatus using an electric knife utilizes various waveforms of high frequency signals, such as a continuous wave, a mixed wave, a burst wave, and the likes, in an operation. Substantially, these high frequency signal waveforms are previously stored in a memory device, and are extracted and used if necessary. Otherwise, high frequency signal waveforms are generated by a divider means, a counter, a multiplier means and the like, on the basis of a source generation signal. In addition, it is needless to say that high frequency signal waveforms can be generated by a combination of those methods.
In addition, in an electric operation apparatus using an electric knife, various high frequency signal waveforms are substantially outputted by one signal device.
Further, in view of the point that an electric knife is a device with a high voltage, as described above, the incision performance and coagulation performance have been improved. However, in order to detect whether or not a high frequency output of a predetermined power is obtained, a method has been taken in which a high frequency output (of several hundreds to several thousands V) is separated with use of an insulating means, and the result obtained therefrom is detected.
Next, a fourth prior art technique will be explained.
Conventionally, to perform incision or to arrest bleeding by coagulation, in a surgical or internal operation, an electric operation apparatus has been used. In this electric operation apparatus, since a high frequency cautery power source apparatus (which will be referred to as only a cautery power source hereinafter) is connected with a treatment tool, and a treatment is performed by outputting a high frequency power from the treatment tool to a portion to be treated, the high frequency power outputted from the cautery power source must be optimally controlled. Therefore, an output current outputted from a high frequency power source for an electric operation and a returning current are detected and compared with each other, to indirectly detect a leakage current or an impedance between the output end of the high frequency power source and the returning end. In addition, in this bipolar mode, a temperature sensor is formed at the top end of an electrode, to detect the temperature added to a tissue surface.
However, even if the output current and the output voltage outputted from a cautery power source are controlled, the density of a current or a power applied to an organism tissue changes due to the area of a treatment tool to be in contact with the treatment portion of a patient and due to characteristics of the organism impedance. Therefore, it is difficult to perform incision or coagulation stanching. In addition, in an electric operation apparatus in which an increase in temperature at a treatment portion is detected by a temperature sensor formed at the top end of an electrode in a bipolar mode thereby to control the coagulation state, noise is mixed into a detection signal, due to the noise level of a high frequency current outputted from the electric operation apparatus itself, so that the detection accuracy is thereby influenced and makes it difficult to perform secure control.
As shown in FIG. 2, an electric operation apparatus 301 conventionally comprises a cautery power source 302 and a treatment tool 303. The cautery power source 302 comprises a power source circuit 322 which generates various voltages by means of an insulating transformer 321 from a power supplied by a commercial power source 304, a signal generator circuit 323 and a waveform shaping circuit 324 which generates signals basing waveform signals of high frequencies corresponding to various treatments such as incision, mixing or coagulation, from the power generated by the power source circuit 322, a high frequency power amplifier circuit 325 which subjects the signals generated by the waveform shaping circuit 324 to high-frequency amplification, a selection circuit 326 which switches the supply destination of the high frequency power amplified by the high frequency power amplifier circuit 325, between circuit of a bipolar mode and a mono-polar mode, and a CPU 327 connected with the selection circuit 326, the power source circuit 322, the signal generator circuit 323, the waveform shaping circuit 324, and the high frequency power amplifier circuit 325, thereby to control each of these circuits.
The selection circuit 326 is connected with a mono-polar output transformer 326a for a mono-polar mode and a bipolar output transformer 326b for a bipolar mode. Further, a mono-polar port 320a as an output end of the mono-polar output transformer 326a is connected with a treatment tool 331 corresponding to the mono-polar mode and with a patient electrode 332 for a returning current. A bipolar port 320b as an output end of the bipolar output transformer 326b is connected with a bipolar treatment tool 333 corresponding to the bipolar mode.
In addition, the CPU 327 is connected with a main panel 328 for selecting various waveforms and for setting various control values of circuits, and respective circuits are controlled by the CPU 327. Further, when an abnormal condition occurs, a treatment is taken in such a manner in which an operator is notified of the abnormal condition by an alarm circuit 329, while an output is stopped by the CPU 327.
As shown in FIG. 3, the characteristic of the high frequency power outputted from the cautery power source 302 changes such that the impedance characteristic of the output transformer such that this characteristic has a peak when the organism impedance is near 300.OMEGA., and the impedance characteristic of the output transformer draws a damping curve from the boundary of the peak value, where the value outputted from an output transformer as an output circuit is set to 150 W or 300 W. Thus, the impedance characteristic of the peak value is changed, depending on the organism impedance, so that the cutting quality of the treatment tool and the stanching performance become unstable. Therefore, when an electric operation apparatus is used to perform a treatment, the output power and the output time with respect to a portion to be treated are set, depending on operator's perception and experiments over years, in view of conditions of a treatment portion observed with eyes.
In order to avoid this problem, Japanese Patent Application KOKOKU Publication No. 5-85177 shows an electric operation apparatus, as shown in FIG. 4, in which the high frequency output characteristic is smoothed to be flat with respect to the organic impedance.
Next, problems of the first prior art technique described above will be explained. In the case where the shapes of the connectors of counter plates are changed so that the type of counter can be distinguished, in order to determine the type of counter, the structure of an associated connecting portion must be complicated and this method therefore leads to an increase in costs. In addition, when the type of counter plate to be used is selected by a user the user may cause an operation error and this method is therefore also not desirable.
Further, problems of the second prior art technique described above will be explained. In accordance with developments in technical improvements in recent years, an electric knife apparatus is used over various fields such as an endoscopic treatment, a surgical operation, and the like. At present, an electric knife apparatus is indispensable in an hospital. Accordingly, in response to such demands, a so-called general purpose electric knife apparatus has been developed which responds to any aspects of techniques and is highly useful.
This electric knife apparatus has a high output power source which deals with a high frequency, and tends to allow a high-frequency current to leak into an unintended route. This high-frequency current becomes a factor which causes an unintended burn in an operator or a patient.
Meanwhile, in the case of the monitor method described in Japanese Patent Application KOKOKU Publication No. 61-32016, a high frequency leakage current can be detected, and besides, safety is ensured somehow since an output value is controlled in accordance with detection results.
However, in a system in which this monitor method is combined with a endoscope, an endoscope code system in which the endoscope body and a counter plate are kept at an equal potential is adopted, in order to collect a high frequency current which once has leaked into the endoscope body and thereby to ensure secure safety for an operator and a patient. In this case, a high frequency current which has once leaked into the endoscope body is collected by the electric knife body through an endoscope code, so that direct risks do not occur with respect to a patient or so. Even so, the monitor system may erroneously operate due to another current which does not pass through a high frequency treatment portion.
In particular, if the tissue resistance has a high impedance or if the load is released, a high frequency current component which flows through an endoscope code is greater than a high frequency current component which flows through a tissue. In this state, a high frequency current flows through a route passing through the endoscope code in an active line, while a current does not substantially or, possibly at all, return to the counter plate side. Then, the value of the ratio IP/IA of the current Ip returning to the counter plate side to a current IA flowing through the active line decreases. Therefore, the output is restricted or stopped regardless of that a dangerous condition does not occur to a patient or an operator. Further, in the case described above, a current flows through the endoscope code, and this current is not for performing a treatment. This means that a wasteful current continues flowing, and serves as a factor which degrades the treatment efficiency.
In addition, in the case of spray coagulation which is considered as particularly useful in a coagulation treatment in a surgical operation, a flow route for a high frequency current must be ensured even when an electrode and a tissue are not in contact with each other. Therefore, the output release voltage must be high enough to cause a breakdown in the air, and the output release voltage should be approximately 6000 to 8000V.sub.P-P. Particularly, in case of spray coagulation, there is a situation that a high frequency leakage current easily leaks into circumstances unintended through a floating capacity.
Further, once a breakdown has occurred between an electrode and a tissue and arc discharging has started, the circuit is brought into a condition in which the circuit is applied with a load, the output voltage decreases and most of the high frequency current flows toward the tissue. Therefore, the high frequency leakage current substantially reaches a negligible level. However, when the distance between the electrode and the tissue is increased to be larger than a certain distance, the arc discharging stops and the load is released, so that the output voltage increases and a situation appears in which a high frequency leakage current easily occurs.
Next, problems of the third prior art technique will be explained. In a conventional electric operation apparatus as described above, since whether out not a high frequency voltage and a high frequency signal are outputted in desired waveforms is not detected when a high frequency signal is actually outputted by an electric knife, a treatment is sometimes insufficient or excessive, e.g., human organisms are sometimes burnt too much or are not cut sufficiently in an operation, so that desired results cannot be achieved in the operation.
Finally, problems of the fourth prior art technique will be explained. In the high frequency output characteristic shown in Japanese Patent Application KOKOKU Publication No. 5-85177, the high frequency output characteristic of the output circuit is fixed and the vicinity of the maximum value indicated by a broken line of the high frequency output is removed and a high frequency output characteristic is obtained, the high frequency output characteristic does not damp due to changes in organism impedance, it is impossible to output the maximum output value set in the electric operation apparatus. Therefore, this apparatus is not suitable for a treatment which requires a high output. In addition, the high frequency output from a cautery power source is not controlled by detecting the organism impedance, but only a high frequency power of a predetermined output value is outputted. Therefore, the apparatus cannot respond to changes in organism impedance and differences in impedance of a treatment tool connected to a cautery power source. Hence, the output time of a high frequency power and the like must be set in view of perception and experiments of an operator.